Alkylphenols find important uses as antioxidants in the fuels, lube, and polymer industries. Isopropylphenols also serve as intermediates for dihydroxybenzenes. Their preparation by alkylation of phenols has been undertaken.
Para-selective alkylation of phenols over the zeolite ZSM-5 has been reported in U.S. Pat. No. 4,391,998.
Naturally occurring and synthetic zeolites have been demonstrated to exhibit catalytic properties for various types of hydrocarbon conversions. Certain zeolites are ordered porous crystalline aluminosilicates having definite crystalline structure as determined by X-ray diffraction studies. Such zeolites have pores of uniform size which are uniquely determined by unit structure of the crystal. The zeolites are referred to as "molecular sieves" because the uniform pore size of a zeolite material may allow it to selectively absorb molecules of certain dimensions and shapes.
By way of background, one authority has described the zeolites structurally, as "framework" aluminosilicates which are based on an infinitely extending three-dimensional network of AlO.sub.4 and SiO.sub.4 tetrahedra linked to each other by sharing all of the oxygen atoms. Furthermore, the same authority indicates that zeolites may be represented by the empirical formula EQU M.sub.2/n O.Al.sub.2 O.sub.3.xSiO.sub.2.yH.sub.2 O
In the empirical formula, M was described therein to be sodium, potassium, magnesium, calcium, strontium and/or barium; x is equal to or greater than 2, since AlO.sub.4 tetrahedra are joined only to SiO.sub.4 tetrahedra, and n is the valence of the cation designated M; and the ratio of the total of silicon and aluminum atoms to oxygen atoms is 1:2. D. Breck, ZEOLITE MOLECULAR SIEVES, John Wiley & Sons, New York p. 5 (1974).
The term "crystalline" used to refer to these materials relates to the ordered definite crystalline structure of the material which is unique and thus identifiable by a characteristic X-ray diffraction pattern.
The term "microporous" as it refers to such material relates to pores, or channels, with diameters of less than 20 Angstroms. Examples of these microporous crystalline materials include crystalline silicates, crystalline alumino-silicates (zeolites), crystalline ALPOs, crystalline SAPO and related compositions and intercalated pillared materials derived from clays, layered silicates and titanates. The crystalline silicate, alumino silicate (zeolites), ALPOs and SAPOs, have pores of uniform size and channel systems which are uniquely determined by unit structure of the material. The uniform pore size and/or channel systems allow such a material to selectively absorb molecules of certain dimensions and shapes. In the art, microporous material having pores, or channels, of less than 20 Angstroms, can be divided into small, medium and large pore by the diameters of those pores, or channels. The pores of the small pore material have an average diameter of less than 5 Angstroms; medium size pores range from an average diameter of about 5 to about 7 Angstroms, and large pore silicates indicates a diameter of greater than about 7. The word "average" is used to refer to diameter to embrace those species in which the pore is elliptical.
Alternatively, the demarcation between small, medium, and large pore materials can be based on the following sorption properties (measured at room temperature for crystallites having a minimum dimension of 0.1 micron):
1. Small pore: n--C.sub.6 /i--C.sub.6 sorption ratio greater than approximately 10. PA1 2. Medium pore: n--C.sub.6 /i--C.sub.6 is less than 10 and n--C.sub.6 /Mesitylene sorption ratio greater than approximately 5. PA1 3. Large pore: n--C.sub.6 /Mesitylene sorption ratio less than approximately 5.
The prior art describes a variety of synthetic zeolites. These zeolites have come to be designated by letter or other convenient symbols, as illustrated by zeolite Z (U.S. Pat. No. 2,882,243); zeolite X (U.S. Pat. No. 2,882,244); zeolite Y (U.S. Pat. No. 3,130,007); zeolite ZK-5 (U.S. Pat. No. 3,247,195); zeolite ZK-4 (U.S. Pat. No., 3,314,752); zeolite ZSM-11 (U.S. Pat. No. 3,709,979) and zeolite ZSM-23 (U.S. Pat. No. 3,076,842), merely to name a few.
ZSM-11 is described in U.S. Pat. No. 3,709,979. That description, and in particular the X-ray diffraction pattern of said ZSM-11, is incorporated herein by reference.
ZSM-12 is described in U.S. Pat. No. 3,832,449. That description, and in particular the X-ray diffraction pattern disclosed therein, is incorporated herein by reference.
ZSM-22 is described in U.S. patent application Ser. No. 373,451 filed Apr. 30, 1982, and now pending. The entire description thereof is incorporated herein by reference.
ZSM-23 is described in U.S. Pat. No. 4,076,842. The entire content thereof, particularly the specification of the X-ray diffraction pattern of the disclosed zeolite, is incorporated herein by reference.
ZSM-35 is described in U.S. Pat. No. 4,016,245. The description of that zeolite, and particularly the X-ray diffraction pattern thereof, is incorporated herein by reference.
ZSM-38 is more particularly described in U.S. Pat. No. 4,046,859. The description of that zeolite, and particularly the specified X-ray diffraction pattern thereof, is incorporated herein by reference.
ZSM-48 is more particularly described in U.S. Pat. No. 4,375,573. Such a description includes the X-ray diffraction pattern for ZSM-48.
Zeolite beta is more particularly described in U.S. Pat. Nos. 3,308,069 and Re. 28,341, each of which is relied upon and incorporated by reference herein.
Zeolite Y can be synthesized with an SiO.sub.2 /Al.sub.2 O.sub.3 ratio up to about 5:1; in order to achieve higher ratios of SiO.sub.2 /Al.sub.2 O.sub.3, various techniques have been developed to remove structural aluminum therefrom.
Crystalline ZSM-5 and its preparation are described in U.S. Pat. No. 3,702,886, the entire disclosure of which is incorporated herein by reference. It has a distinctive X-ray diffraction pattern which identifies it from other known crystalline silicates. A crystalline silicate composition having the structure of ZSM-5 is described in U.S. Pat. No. 29,948, the entire disclosure of which is incorporated herein by reference.
The incorporation of the identified patents and patent applications should not be construed as limiting the disclosed crystalline zeolites to those having the specific silica-alumina mole ratios discussed therein, it now being known that such zeolites may be substantially aluminum-free and yet, having the same crystal structure as the disclosed materials, may be useful or even preferred in some applications. It is the crystal structure, as identified by the X-ray diffraction "fingerprint", which establishes the identity of the specific crystalline zeolite material. The crystal structure of known zeolites may include framework elements, other than or in addition to silicon and aluminum, without changing its identification by the X-ray diffraction "fingerprint"; and these gallium, boron, iron and chromium containing silicates and aluminosilicates may be useful, or even preferred, in some applications described herein.
The silicon/aluminum atomic ratio of a given zeolite is often variable. For example, zeolite X can be synthesized with silicon/aluminum atomic ratios of from 1 to 1.5, while that ratio in zeolite Y is from 1.5 to 5. In some zeolites, the upper limit of the silicon/aluminum atomic ratio is unbounded. ZSM-5 is one such example wherein the silicon/aluminum atomic ratio is at least 2.5 and up to infinity. U.S. Pat. No. 3,941,871, reissued as RE. 29,948, discloses a porous crystalline silicate made from a reaction mixture containing no deliberately added aluminum and exhibiting the X-ray diffraction pattern characteristic of ZSM-5.
The exact chemical make-up of zeolites including ZSM-5 can determine the nature of its activity in a particular catalysis. In the art, zeolites are a subclass of crystalline microporous silicates. Zeolites can contain aluminum as well as silicon. The chemical make-up of the zeolite, in terms of its silica/alumina atomic ratio is of practical significance. In some zeolites, the upper limit of the silicon/aluminum atomic ratio is unbounded. ZSM-5 is one such example wherein the silicon/aluminum atomic ratio is at least 2.5 and up to infinity. By way of illustration, U.S. Pat. No. 3,941,871, reissued as RE 29,948, discloses a porous crystalline silicate made from a reaction mixture containing no deliberately added aluminum and exhibiting the X-ray diffraction pattern characteristic of ZSM-5 zeolites.
Zeolites can be acidic or non-acidic, depending on the framework aluminum content and on the amount of compensating cations, such as Na.sup.+, K.sup.+, etc.